Even if Sears Holdings’ days are numbered, the retailer’s impact on Chicago’s skyline seems likely to last generations.

Many of the city’s biggest and most recognizable buildings sprung from the decades when Sears, Roebuck & Co. and its rivals — including Montgomery Ward & Co., Marshall Field & Co. and Carson Pirie Scott & Co. — made Chicago the capital of department store chains and mail-order catalogs.

Those properties have been redeveloped from their initial uses, finding new relevance.

That includes Chicago’s two largest office buildings by square feet, the Merchandise Mart and Willis Tower, and the city’s largest data center. These days it’s difficult to imagine a company single-handedly creating the next 110-story Sears Tower (now Willis Tower) or two-block-long Merchandise Mart.

Only one comes to mind.

Amazon, which has been described as a modern, online version of Sears, just so happens to be on the hunt for a sprawling second headquarters.

HQ2, as Amazon is calling it, is the rare modern version of a retailer-driven development that could permanently change the face of the North American city it selects to add 50,000 new jobs. Seattle-based Amazon plans to announce its pick from 20 contenders, including Chicago, by the end of this year.

No matter what happens with Amazon’s search, or with Sears’ efforts to emerge from Chapter 11 bankruptcy, many of Chicago’s most important places to do business likely will remain the properties created directly or indirectly from Chicago’s retail heyday.

Chris Sweda/Chicago Tribune

Digital art displays are projected on the facade of the Merchandise Mart in downtown Chicago during the launch of Art on theMart on Sept. 29, 2018.

Digital art displays are projected on the facade of the Merchandise Mart in downtown Chicago during the launch of Art on theMart on Sept. 29, 2018. (Chris Sweda/Chicago Tribune)

MERCHANDISE MART

Marshall Field & Co. built the Merchandise Mart as a massive wholesale marketplace for retailers.

The 4.2 million-square-foot building, which opened on the north banks of the Chicago River in 1930, was the world’s largest until the Pentagon was completed more than a decade later.

The art deco building later was used for government offices during World War II, before eventually becoming home to interior design showrooms and trade shows.

In recent years, as demand for River North office space has boomed, the building’s owner has converted swaths of showrooms into higher-rent offices.

The 25-story building has emerged as a top destination in the technology sector, with tenants including Motorola Mobility, Yelp, Braintree and the 1871 tech incubator.

The building, which owner Vornado Realty Trust now markets as theMART, also is known for big corporate relocations—capturing Motorola Mobility from Libertyville, Conagra Brands from Omaha, Neb., and Beam Suntory from Deerfield. It has its own CTA train stop to serve 10,000 workers and an average 35,000 total daily visitors per day.

The riverfront behemoth recently added another use to its varied history: blank canvas. In September’s inaugural Art on theMART public art event, colorful video art was projected onto the 2½-acre south side of the building’s exterior.

WILLIS TOWER

When Sears Tower opened in 1973, Chicago became home to the world’s tallest skyscraper—a distinction that lasted 24 years.

At the height of its greatness, Sears, Roebuck and Co. moved its headquarters from a sprawling Homan Square campus to the 1,451-foot-tall tower on Wacker Drive.

The 110-story building has undergone a series of reinventions, starting when Sears moved its headquarters to suburban Hoffman Estates in 1992.

Chicago’s tallest skyscraper experienced leasing difficulties after the Sept. 11, 2001, terrorist attacks stoked fears that the skyscraper could be a target. But it has always remained a major tourist destination, and today it is home to more than 15,000 workers, with huge tenants including the headquarters of United Airlines.

Although its identity formally changed in a 2009 naming-rights deal with tenant Willis Group Holdings, an insurance broker, many Chicagoans refuse to call the skyscraper anything but Sears Tower.

Private-equity giant Blackstone Group bought Willis Tower for $1.3 billion in 2015. It remains the highest price ever paid for a Chicago building, or for any office building outside New York.

Blackstone is pouring another $500 million into a renovation and expansion, which will add 300,000 square feet of restaurant, retail and entertainment space at the base of the tower. When the project is completed in late 2019, the tower will have expanded to 4.5 million square feet.

Phil Velasquez/Chicago Tribune

The lobby of the long-vacant Old Main Post Office, which is being redeveloped by New York-based 601W into modern offices and retail space. on Sept. 22, 2017.

The lobby of the long-vacant Old Main Post Office, which is being redeveloped by New York-based 601W into modern offices and retail space. on Sept. 22, 2017. (Phil Velasquez/Chicago Tribune)

OLD POST OFFICE

It was no coincidence that the world’s largest post office was created in Chicago.

The United States Postal Service needed a one-of-a-kind facility to process incoming mail orders, and to ship out mountains of packages from the warehouses of Montgomery Ward, Sears, Spiegel, and many others.

The old main post office, which was expanded in phases, was completed in the 1930s.

It became obsolete by the 1990s, and after the Postal Service moved next door, sat vacant for more than two decades when plans by developers including eccentric British investor Bill Davies never panned out.

New York-based 601W Cos. bought the art deco building for $130 million in 2016, and is in the midst of an $800 million-plus project to convert the structure into 2.8 million square feet of modern offices, restaurants, shops and amenities including a 4-acre rooftop park.

When completed, it will become the third-largest office building in Chicago, by total square feet, according to real estate brokerage CBRE.

The redevelopment received a big boost in June, when Deerfield-based drugstore chain Walgreens confirmed plans to move more 1,800 workers into a 200,000-square-foot space in the building, which is now called the Old Post Office.

Chicago’s bid for HQ2 included an option that would have combined spaces in several buildings, including the Old Post Office and Willis Tower. Amazon officials appear to have narrowed their Chicago options to proposed ground-up developments.

If ever a building has evolved with the times, it’s the former R.R. Donnelly and Sons printing facility at 350 E. Cermak Road.

The 1.1 million-square-foot building near McCormick Place once churned out hefty printing jobs like Sears catalogs and phone books.

These days, the building is lined with servers to support the ever-growing internet usage that eliminated the need for most of those printing jobs.

If you send an email, stream a movie or buy something online from anywhere in the Midwest today, it’s likely to pass through Lakeside Technology Center. The facility is considered the nexus of Midwest connectivity, and it’s one of the largest data centers in the world.

Owner Digital Realty wants to make it even bigger, with plans to build a 700,000-square-foot annex across the street.

Once upon a time, workers at Montgomery Ward’s Catalog House wore roller skates so they could quickly fill mail orders from expansive rows of merchandise. It was a precursor to today’s fast-paced e-commerce distribution centers that in some cases deliver orders within hours.

Montgomery Ward’s multi-building riverfront complex was redeveloped in the early 2000s into residences and a 1.65 million-square-foot office building.

As many technology and creative firms sought out older buildings with ultra-wide floor plates, the building attracted tenants including the headquarters of Groupon and other tech firms created by the firm’s founders, such as Echo Global Logistics and Uptake Technologies. The building, which has a water taxi station and a new roof deck, also is home to the Big Ten Network’s offices and studios.

About 7,000 people work in the building, which opened in 1908. It is Chicago’s sixth-largest office building, according to CBRE.

Chicago developer Sterling Bay in February bought the building for $510 million. The seller was Equity Commonwealth, a real estate investment trust led by Sam Zell.

Jose M. Osorio/Chicago Tribune

The Fields, the former Marshall Field's warehouse now a Merit Partners development in Chicago on March 19, 2015.

The Fields, the former Marshall Field's warehouse now a Merit Partners development in Chicago on March 19, 2015. (Jose M. Osorio/Chicago Tribune)

THE FIELDS

A 22-acre campus of warehouses once used by Olson Rug & Carpet, and later by Marshall Field’s, is in the midst of a redevelopment into an eclectic mix of new uses.

The Fields, as it is now called, also includes a 123-unit loft apartment project in a joint venture with another Chicago developer, Hubbard Street Group.

Knickpoint Ventures recently said it bought Merit’s stake in the 1.5 million-square-foot property. The New York-based firm will take over finding tenants for the approximately one-third of the property that has yet to be leased or sold.

Jose M. Osorio/Chicago Tribune

The former Sears administration administration building in Chicago's Homan Square neighborhood on Jan. 11, 2017.

Other notable properties with roots in Chicago’s department-store glory days include Sears’ former 3 million-square-foot Homan Square office and printing campus on the West Side, part of which last year was converted into affordable housing units.

Downtown, Marshall Field’s former State Street building lives on as a Macy’s flagship. Macy’s earlier this year announced a $30 million deal to sell the upper half of the 14-story building to Toronto-based Brookfield Asset Management, which plans to convert the underutilized floors to offices.

Farther south on State Street, a onetime Carson Pirie Scott flagship is now a Target store within the Sullivan Center, a series of combined buildings designed by architect Louis Sullivan. Old Post Office developer 601W this year bought the office portion of the Sullivan Center for $176 million.

Also downtown, a former Butler Bros. mail-order warehouse at 111 N. Canal St. is now home to office tenants including Twitter, Uber and the headquarters of in-flight wireless provider Gogo.